Cutter bar with speed tip

ABSTRACT

A cutter bar for a chain saw and having a detachable nose assembly at the outer end of the bar which includes an idler sprocket so mounted that it carries the chain of the saw around the effective outer end or nose end of the bar clear of the side edges of this end, said assembly being no thicker than the guide bar. The cutter bar includes brace means for the assembly, and means for fixedly interconnecting these elements.

D United States Patent 1 1 1111 3,762,047

Scott-Jackson 1 Oct. 2, 1973 [54] CUTTER BAR WITH SPEED TIP 2,888,964 6/1959 Mall 30/384 2,316,997 4/1943 Smith 30/385 [751 f'l' Scotti-lacks, Bumaby' 2,693,206 11 1954 Anttonen 30/284 Br1t1sh Columbla, Canada [73] Assignee: Windsor Machine Company Limited, P i E i Donald R, Schran British Columbia, Canada Attorney-Kellard A. Carter [22] Filed: Feb. 7, I972 {21] App]. No; 223,994 ABSTRACT A cutter bar for a chain saw and having a detachable 52 us. (:1. 30/385, 83/820 assembly the end the bar which {5 1] H B27) 17/04 cludes an idler sprocket s0 mounted that it carries the [58] Field of Search 143/32 R 32H- Chai" ("the Saw around cffcctivc outer end 0r 30/384 385 383, 83/820 end of the bar clear of the side edges of this end, said assembly being no thicker than the guide bar. The cut- [56] References Cited ter bar includes brace means for the assembly, and

UNITED STATES PATENTS 3/1964 Ekrud 30/384 means for fixedly interconnecting these elements.

13 Claims, 5 Drawing Figures CUTTER BAR WITH SPEED TIP This invention relates to cutter bars for use inchain saws and having improved outer or nose ends.

As is well known, the saw chain bar is used to locate, support and guide the saw chain throughout its periphery while cutting wood. This can be done in the longitudinal or transverse direction of the wood grain. During the cutting action of the saw chain the nose end of the saw bar is subjected to great strain and friction, and this results in severe overheating and wear of the metal forming the bar. In addition this condition results in reducing the applied power available for wood cutting.

In the past, some efforts have been made to alleviate these problems by providing a pulley or sheave at the outer end of the guide bar and around which the saw chain travels. This is an improvement over the solidend bars, but has left a lot to be desired, as evidenced by the fact that the pulley is mounted in an assembly which is removably mounted on the end of the guide bar for easy replacement. Pulley and sheave assemblies have usually been provided with either side plates that overlap the surfaces of the saw bar, or a centrally located supporting member supporting a fabricated pulley which also overlapped the surfaces of the saw bar. The assembly being thicker than the supporting guide bar itself necessitated the cutting of a wider kerf to clear said members, or resulted in a consistant binding condition while cutting.

The present invention eliminates or greatly reduces the problems set out above. A cutter bar according 'to this invention has a nose assembly secured to the outer end thereof, this assembly forming the effective outer Y or nose end of the bar. A sprocket is so located within the assembly as to carry the saw chain around the end of the assembly with the portions of the chain, which travel or ride on the side or rail edges of the guide bar, clear of the side edges of the assembly. This greatly reduces the friction created at the nose end of the bar. A very important feature is that the nose assembly is no thicker than the guide bar, and yet the assembly interlocks with the bar so that the assembly is well supported at the bar end. Bracing means is provided between the bar and the assembly, and the construction is such that, although the assembly is fixedly secured to the bar, it can easily be removed for replacement or when it is necessary to use a sprocket of a different pitch.

A chain saw cutter bar in accordance with the present invention comprises an elongated guide bar having a slot in each of opposite side edges thereof in which the drive lugs or tangs of a saw chain can travel with portions of said chain riding on the side edges, a nose assembly secured to and projecting beyond an outer end of the bar and in the plane of said bar, said assembly being no thicker than the guide bar, and a sprocket rotatably mounted within the nose assembly having a pitch to receive the drive lugs or nose and positioned to guide the saw chain around said assembly with said chain portions clear of the assembly.

This nose assembly includes parallel face plates with the sprocket rotatably mounted therebetwe'en. Connectors extend from these plates into recesses formed in the opposite faces of the guide bar at the end thereof,

and overlap a portion of the bar without projecting from the bar faces, these connectors being secured to said bar portion.

An example of this invention is illustrated in the accompanying drawings, in which FIG. 1 is a reduced side view of a cutter bar in accordance with this invention,

FIG. 2 is an enlarged side elevation of the outer or nose end of the bar, with part of the nose assembly broken away,

FIG. 3 is a longitudinal section taken on the line 3-3 of FIG. 2,

FIG. 4 is a cross section taken on the line 44 of FIG. 2, and

FIG. 5 is an exploded perspective view of the nose assembly and the adjacent end of the bar.

Referring to the drawings, 10 is a chain saw cutter bar which is adapted to be connected to the power unit of a chain saw in the usual manner. This bar has the usual opposite side edges 12 and 13 with slots 16 and 17 therein. A standard saw chain 20, shown in broken lines in FIG. 2, has drive links with lugs or tangs 22 which ride in slots 16 and 17 as the chain moves around the guide bar. As the chain travels along edges 12 and 13, portions thereof, usually side links 23, ride on said edges. The drive arrangement for the chain has not been shown since it is well known, and the description of it is not required herein.

A nose assembly 28 is secured to and projects beyond the outer end 29 of bar l0. This assembly is made up of a pair of spaced-apart, parallel face plates 32 and 33. These platesare spaced apart by an inner race 36, said plates being secured to each other and to the race in any suitable manner, such as by a plurality of rivets 37 extending through the plates and the race. A plurality of bearings 40 surround race 36 and carry an idler sprocket 42 which has a pitch suitable for the chain 20. Sprocket 42 is mounted between plates 32 and 33 for rotation around a central axis 44.

Face plates 32 and 33 have edges 46 which, when assembly 28 is mounted on bar 10, extend outwardly from edge 12 of the bar and around in a curved section 47 centered on axis 44 and to the other edge 13 of the bar. The radius of curve 47 is less than the radius of sprocket 42 so that the teeth 49 of the sprocket project outwardly from between the face plates as they travel around curve 47.

As chain 20 travels around the curved outer end of nose assembly 28, which is the effective outer end of bar 10, the tangs 22 of the chain fit between the sprocket teeth 49. At the same time, the teeth 49 carry the chain so that the portions of side links 23 are free of the curved portion of edge 47 of the face plates as they travel around the curved end. This greatly reduces the friction of the chain travelling around the effective end of the guide bar.

Rectangular recesses 52 and 53 are formed in opposite faces of bar 10, and extend longitudinally thereof and open out from the end 29 of the bar. A portion of bar 10 is left between recesses 52 and 53 in the form of a flange or web 55. Although not absolutely necessary, it is desirable to cut web 55 to form a relatively large slot 58 therein which .is substantially rectangular in shape and opens out through the end 29 of the bar. This slot leaves web 55 in the form of a flange extending along the boundary edges of recesses 52 and 53. Edges 59 and 60 of web 55 form opposed boundaries for slot 58.

Connectors in the form of extensions 62 and 63 project from plates 32 and 33, respectively, and are shaped to fit within recesses 52 and 53 on opposite sides thereof and overlapping flange 55. A spacer 65 is positioned between connectors 62 and 63 and is shaped to fit into slot 58. This spacer has a widened end 66 which is located between face plates 32 and 33, said end being curved as at 67 so as to be as close as possible to but spaced from sprocket 42. The connectors and spacer 65 is secured together in any suitable manner, and in the illustrated example, a plurality of rivets 70 extend through connectors 62 and 63 and spacer 65, and rivets 71 extend through plates 32 and 33 and connector end 66 for this purpose. Spacer 65 preferably is formed with machined edges 72 and 73 which fit against edges 59 and 60 of web 55.

Plates 32 and 33 have inner edges 74 that abut against squared ends 75 on the end of guide bar 10.

When assembly 28 is mounted in place, plate edges 74 abut against the squared ends 75 of the bar, spacer 65 fits in slot 58, and connectors 62 and 63 overlap flange 55 and fit within the bar recesses 52 and 53. Assembly 28 is held in position by a single rivet 79 which extends through the two connectors and flange 55.

When cutter bar is ready for use, chain extends along its opposite edges 12 and 13 and around the curved end 47 of assembly 28. The drive lugs or tangs 22 of the chain ride in bar slots 16 and 17, while the side links 23 ride on bar edges 12 and 13. However, sprocket 42 is so positioned that its teeth 49 lift the side links away from the curved end 47 as the chain moves around said curved end, thereby reducing all friction at this curved end. Although nose assembly 28 is subjected to great strain as the cahin cuts into wood, the assembly is firmly secured to and braced by the outer end of bar 10, even though the assembly is secured to the bar by rivet 79 only. The ends 74 of the face plates bearing against the squared ends 75 of the bar brace the assembly against forces that would tend to rock the assembly laterally relative to the bar and in the plane of the latter. These forces are also resiste'd particularly by the fit of edges 72 and 73 of spacer 65 against edges 59 and 60 of web 55, and also the fit of connector extensions 62 and 63 in bar recesses 52 and 53. Flange 55 not only enables the assembly to be connected to the bar, but it braces the assembly against any forces tending to swing it out of the plane of the guide bar. If it is necessary to change assembly 28 for replacement or for one having a sprocket of a different pitch, it is only necessary to remove rivet 79. Thus, the sprocket can be easily and quickly changed. Furthermore, idler sprocket 42 so reduces the friction at the nose end of the bar that the saw chain runs much faster and thereby cuts more quickly through the wood than it otherwise would, or less power can be used to attain the same cutting speed.

I claim:

1. A chain saw cutter bar comprising an elongated guide bar having a slot in each of opposite side edges thereof in which the drive tangs of a saw chain can travel with portions of said chain riding on the side edges, rectangular recesses in opposite faces of the bar and opening out from an outer end thereof, each of said recesses being spaced from the opposite side edges of the bar and having opposed edges extending longitudinally of the bar, a nose assembly projecting outwardly beyond the outer end of the bar and in the plane thereof, said assembly being no thicker than the bar and comprising a pair of spaced-apart face plates secured to each other, a connector extending from each plate shaped to fit snugly within one of said recesses, means securing said connectors to the bar, said plates having curved edges extending from one of said side edges of the bar around to the other of said side edges thereof, a sprocket rotatably mounted between and completely within the face plates and having a pitch to receive drive tangs projecting inwardly between the face plates and positioned to guide the saw chain around said assembly with said chain portions clear of the curved edges of the plates.

2. A cutter bar as claimed in claim 1 including an inner race extending between and fixedly secured to the face plates, and bearings around the periphery of the race, said sprocket being carried by the bearings.

3. A cutter bar as claimed in claim 1 including an inner race extending between and fixedly secured to the face plates, and bearings around the periphery of the race, said sprocket being carried by the bearings.

4. A chain saw cutter bar as claimed in claim 1 including squared ends on the outer end of the guide bar extending outwardly from the recesses thereof to the bar side edges, and shoulders formed on said face plates on opposite sides of the connectors thereof and abutting against the squared ends of the bar.

5. A chain saw cutter bar as claimed in claim 4 including a flange projecting from the bar into the recesses thereof along the edges defining said recesses and substantially midway between the bar faces, said connectors overlapping the flange, a slot in said flange extending longitudinally of the bar, and a spacer shaped to fit snugly in said slot and secured to the face plate connectors.

6. A chain saw cutter bar as claimed in claim 4 in which said means securing the connectors to the bar comprises a rivet extending through both connectors and the flange therebetween.

7. A chain saw cutter bar comprising an elongated guide bar having a slot in each of opposite side edges thereof in which the drive tangs of a saw chain can travel with portions of said chain riding on the side edges, rectangular recesses in opposite faces of the bar and openingout from an outer end thereof, a flange projecting from the bar into the recesses around the edge defining the recesses and substantially midway between the bar faces, a nose assembly projecting outwardly beyond the outer end of the bar and in the plane thereof, said assembly being no thicker than the bar and comprising a pair of spaced-apart face plates secured to each other, a connector extending from each plate into and fitting within one of said recesses and overlapping said flange, means securing the connectors to the flange, a sprocket rotatably mounted between the face plates and having a pitch to receive the drive tangs and positioned to guide the saw chain around said assembly with said chain portions clear of the assembly.

8. A cutter bar as claimed in claim 7 in which said securing means comprises a rivet extending through both connectors and the flange therebetween.

9. A cutter bar as claimed in claim 7 including a spacer between and secured to the face plate connectors, said spacer fitting in a slot within the flange.

10. A cutter bar as claimed in claim 7 in which said face plates have ends bearing against squared ends on the guide bar.

11. A cutter bar as claimed in claim 7 including a spacer between and secured to the face plate connec- 13. A cutter bar as claimed in claim 1 including a spacer between and secured to the face plate connectors said spacer fitting snugly within a slot in the flange, and said face plates having ends bearing against squared ends on the guide bar. 

1. A chain saw cutter bar comprising an elongated guide bar having a slot in each of opposite side edges thereof in which the drive tangs of a saw chain can travel with portions of said chain riding on the side edges, rectangular recesses in opposite faces of the bar and opening out from an outer end thereof, each of said recesses being spaced from the opposite side edges of the bar and having opposed edges extending longitudinally of the bar, a nose assembly projecting outwardly beyond the outer end of the bar and in the plane thereof, said assembly being no thicker than the bar and comprising a pair of spaced-apart face plates secured to each other, a connector extending from each plate shaped to fit snugly within one of said recesses, means securing said connectors to the bar, said plates having curved edges extending from one of said side edges of the bar around to the other of said side edges thereof, a sprocket rotatably mounted between and completely within the face plates and having a pitch to receive drive tangs projecting inwardly between the face plates and positioned to guide the saw chain around said assembly with said chain portions clear of the curved edges of the plates.
 2. A cutter bar as claimed in claim 1 including an inner race extending between and fixedly secured to the face plates, and bearings around the periphery of the race, said sprocket being carried by the bearIngs.
 3. A cutter bar as claimed in claim 1 including an inner race extending between and fixedly secured to the face plates, and bearings around the periphery of the race, said sprocket being carried by the bearings.
 4. A chain saw cutter bar as claimed in claim 1 including squared ends on the outer end of the guide bar extending outwardly from the recesses thereof to the bar side edges, and shoulders formed on said face plates on opposite sides of the connectors thereof and abutting against the squared ends of the bar.
 5. A chain saw cutter bar as claimed in claim 4 including a flange projecting from the bar into the recesses thereof along the edges defining said recesses and substantially midway between the bar faces, said connectors overlapping the flange, a slot in said flange extending longitudinally of the bar, and a spacer shaped to fit snugly in said slot and secured to the face plate connectors.
 6. A chain saw cutter bar as claimed in claim 4 in which said means securing the connectors to the bar comprises a rivet extending through both connectors and the flange therebetween.
 7. A chain saw cutter bar comprising an elongated guide bar having a slot in each of opposite side edges thereof in which the drive tangs of a saw chain can travel with portions of said chain riding on the side edges, rectangular recesses in opposite faces of the bar and opening out from an outer end thereof, a flange projecting from the bar into the recesses around the edge defining the recesses and substantially midway between the bar faces, a nose assembly projecting outwardly beyond the outer end of the bar and in the plane thereof, said assembly being no thicker than the bar and comprising a pair of spaced-apart face plates secured to each other, a connector extending from each plate into and fitting within one of said recesses and overlapping said flange, means securing the connectors to the flange, a sprocket rotatably mounted between the face plates and having a pitch to receive the drive tangs and positioned to guide the saw chain around said assembly with said chain portions clear of the assembly.
 8. A cutter bar as claimed in claim 7 in which said securing means comprises a rivet extending through both connectors and the flange therebetween.
 9. A cutter bar as claimed in claim 7 including a spacer between and secured to the face plate connectors, said spacer fitting in a slot within the flange.
 10. A cutter bar as claimed in claim 7 in which said face plates have ends bearing against squared ends on the guide bar.
 11. A cutter bar as claimed in claim 7 including a spacer between and secured to the face plate connectors said spacer fitting snugly within a slot in the flange, and said face plates having ends bearing against squared ends on the guide bar.
 12. A cutter bar as claimed in claim 1 in which said securing means comprises a rivet extending through both connectors and the flange therebetween.
 13. A cutter bar as claimed in claim 1 including a spacer between and secured to the face plate connectors said spacer fitting snugly within a slot in the flange, and said face plates having ends bearing against squared ends on the guide bar. 